Rotor sail and ship with a rotor sail

ABSTRACT

A rotor sail is provided having a base ( 2 ) and a rotary cylinder ( 3 ) mounted on the base ( 2 ) in a manner permitting rotation about its longitudinal axis designed as the rotor axis (r), and a drive ( 5 ) for rotating the rotary cylinder ( 3 ). An enclosing outer surface ( 4 ) of the rotary cylinder serves as a wind-exposed surface in operation. So that the rotor sail can be operated in a more environmentally friendly manner, it is provided with a photovoltaic system ( 7 ) having solar cells ( 8 ) to generate electric energy for the drive ( 5 ) having an electric motor ( 6 ). The solar cells ( 8 ) are located in the rotary cylinder ( 3 ) and have photoelectrically active layers facing toward the enclosing outer surface ( 4 ). The rotary cylinder ( 3 ) has a sleeve ( 9 ) which is transparent, at least in an area covering the solar cells ( 8 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 of International Application No.PCT/DE2006/001821, filed Oct. 17, 2006, which was published in theGerman language on Apr. 26, 2007, under International Publication No. WO2007/045220 A1 and the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The invention relates to a rotor sail with a base, a rotary cylinder,which is mounted on the base in a manner permitting rotation about itslongitudinal axis designed as the rotor axis, and whose enclosing outersurface serves as a wind-exposed surface in operation, and a drive forrotating the rotary cylinder.

A rotor sail of this kind is also known as a Flettner rotor, whichrotates when driven by a drive. When the wind flows against the rotatingrotor sail, a force transverse to the direction of flow of the wind isformed in accordance with the so-called Magnus effect as a result ofsurface friction between the rotor sail and the air flowing around it,as well as within the air adjacent to the rotor sail. The environmentalpollution caused by the drive is, however, a disadvantage.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is therefore to develop the rotor sail insuch a way that it can be operated in a more environmentally friendlymanner.

According to the invention, the object is achieved by providing aphotovoltaic system with solar cells to generate electric energy for thedrive, where the drive includes an electric motor, by locating the solarcells in the rotary cylinder, by facing the photoelectrically activelayers of the solar cells toward the enclosing outer surface, and bydesigning the sleeve of the rotary cylinder as transparent, at least inthe area covering the solar cells. The photovoltaic system thus servesto generate electric current, which can be used directly, via acorresponding control system, to operate the drive, such that the rotorsail, like a conventional wind sail, can be operated in the windcompletely independently of additional systems, such as dieselgenerators or the like. Since a rotor sail of this kind is independentof an additional fuel supply, it can also be used in remote regions.Arranging the solar cells in the rotary cylinder also protects them atthe same time. Moreover, this does not require any increase in sizecompared to a conventional rotor sail. The photovoltaic system can evenbe installed in existing rotor sails. For adaptation to the directcurrent generated by the solar cells, the electric motor can be designedas a DC motor.

Expediently, the end face of the rotary cylinder that is free inoperation can also be of transparent design, at least in its radiallyouter areas. This can further increase the solar irradiation toward thesolar cells.

As on the familiar rotor sail, the so-called Flettner rotor, the endfaces of the rotary cylinder preferably project radially beyond thecylindrical sleeve of the rotary cylinder, as a result of which morefavorable flow conditions can be achieved, particularly on the end areasof the surface of the cylindrical sleeve of the rotary cylinder adjacentto the end faces, when the wind flows against the rotor sail.

The solar cells are preferably located on the outer side of a core inthe rotary cylinder. In this context, the core should provide a sturdysupport for the solar cells. Furthermore, the longitudinal axis of thecore should be identical with the rotor axis of the rotor sail.

The core should preferably have a round or polygonal cross-section. Ahighly symmetrical core is proposed here as the support for the solarcells, thus enabling the possible peripheral arrangement and orientationof the solar cells to be symmetrical and uniform, such that identicalconditions for generating electric current via the solar cells can becreated over the periphery.

In this context, the cross-section of the core is preferably of circulardesign. In this embodiment, the core can be designed as a cylinder whosesleeve is located parallel to the sleeve of the rotary cylinder, thusresulting in advantages regarding design and uniform generatingconditions.

In one embodiment of the core, the core can be designed to taperprismatically or conically toward the top over its height in operatingposition. As a result, the solar cells can be arranged on the core at amore favorable angle to the incident solar radiation in operatingposition, thus making it possible to increase the efficiency of thephotovoltaic system.

To this end, the core can be favorably designed as a truncated pyramidin the case of a prismatic taper, or as a truncated cone in the case ofa conical taper.

In one embodiment of the core, the core can have a variable openingangle, formed between the center axis and the side face. In this way,the orientation of the solar cells located on the core can be optimizedin accordance with a current mean solar altitude, or a mean solaraltitude determined by the geographical location.

The core can preferably be mounted in non-rotating fashion relative tothe base, meaning that the rotary cylinder rotates about a static core.The result of this is that the sun only ever illuminates one side of thecore, meaning that only this side would need to be equipped with solarcells. To this end, a device can be provided that orients the core inaccordance with the current direction of the incident solar radiation,in such a way that the surface of the solar cells is positioned asperpendicular as possible to the direction of the incident solarradiation. To this end, the core can also have a planar, flat body,whose dimensions, for preferred maximum exploitation of the availablearea in the rotary cylinder, can be designed to be slightly smaller thanthe height and inside diameter of the rotary cylinder. In the case ofnon-rotating mounting, it is necessary for the sleeve of the rotarycylinder to be of transparent design over its circumference at the levelof the solar cells.

In another embodiment, the core can be mounted in a manner permittingrotation about its longitudinal axis. To this end, the core can beexpediently connected to the rotary cylinder in non-rotating fashion. Asa result, the solar cells located on the core are stationary in relationto the section of the sleeve of the rotary cylinder that covers them.The rotary cylinder and the core with the photocells thus form a commonrotary body whose inert mass is increased compared to the rotarycylinder alone, meaning that uniform operation, i.e., more uniformrotation of the rotary cylinder, is possible in the case of fluctuatingwinds. To simplify the structural design of the rotor sail and formaximum exploitation of the space inside the rotary cylinder, the coreand the rotary cylinder can have common end faces.

In another embodiment, the solar cells can be located directly on theenclosing inner surface of the rotary cylinder. As a result, the rotarycylinder can serve simultaneously as the support and a guard for thesolar cells. This moreover greatly simplifies the structure of the rotorsail as a whole.

It is furthermore possible, in the case of particularly stable modules,such as those marketed by the Bayer company under the trademarkMAKROLON, for the rotor sleeve to be constructed, at least in segmentsor in rings, from these stable modules or from the corresponding solarcells.

The solar cells can be designed as thin-film solar cells, for example.These thin-film solar cells are usually flexible and can thus easily beapplied to a round core or the inner surface of the sleeve of the rotarycylinder. Depending on the respective application or the design of thesolar sail, particularly of the core, different types of solar cell areopen to consideration as optimum types.

Solar cells that are inflexible, due to being thicker, requireapplication to a plane supporting surface, meaning that the embodimentsof the core with prismatic side faces are open to consideration in thiscase. However, these inflexible solar cells usually demonstrate greaterefficiency. The solar cells can be made, for example, using amorphoussilicon, cadmium telluride (CdTe), copper-indium-diselenide (CuInSe₂;CIS), copper-indium-gallium, or the like as the active layers. However,since a relatively large sleeve surface of the core or inside surface ofthe sleeve of the rotary cylinder can be available on relatively largerotor sails, the solar cells can also have flexible, semiconductiveorganic polymers in the active layer, these currently being a low-costalternative to inflexible solar cells, but demonstrating far lowerefficiency.

With today's solar cells, the photovoltaic system can achieve an outputof roughly 150 W/m², which can be fed to a corresponding DC motor.Particularly in the embodiments in which the core is connected to therotary cylinder in non-rotating fashion, the axis of rotation of themotor itself can be arranged in such a way that the motor drives therotary cylinder and the core directly.

The electric drive is preferably located in the base, where the axis ofrotation of the rotor sail can extend into the base. The drive isprotected as a result. In addition, a storage device can be provided tostore the energy generated by the photovoltaic system. It is possible tostore surplus electric energy generated in calm weather or when therotary cylinder is not in operation, for example. The storage device canexpediently have storage batteries as storage media. The stored energycan serve to supply the drive, particularly at night or in the case ofundersupply of the drive due to a greatly reduced level of incidentlight. This surplus electric energy can, however, also be used, e.g., inthe case of a lull, to operate other units, e.g., on a ship to drive anelectrically powered propeller or for a seawater desalination unit forsupplying the ship with fresh water.

For use in the rotor sail, a customary control system for a photovoltaicsystem can have additional open-loop and/or closed-loop control elementsthat control the electric energy generatable and generated by thephotovoltaic system, particularly its feeding into and tapping from theelectric drive, as well as into and from the storage device. In thiscontext, closed-loop control can ensure, for example, a constantrotational speed of the rotary cylinder or, by measuring the wind speed,regulate the rotational speed of the rotary cylinder in such a way thata roughly constant force perpendicular to the direction of the wind isgenerated by the Magnus effect. In this respect, a peripheral speed ofthe rotary cylinder corresponding to three to five times the wind speedis considered to be a favorable value. The drive can be designed in sucha way that, during deceleration of the rotary cylinder, it acts as agenerator, whose generated energy can be stored.

Less preferred because of the currently higher technical outlay, butnevertheless considered, is the use of a hybrid motor instead of, or inaddition to, the electric motor, where the electric energy generated bythe solar cells is used to hydrolyze water and store hydrogen. To thisend, a storage facility for storing the generated hydrogen should alsoexpediently be provided. As is generally known, the hydrogen can beburned in the hybrid motor in an environmentally friendly manner,producing water.

The rotor sail can preferably be installed in a vehicle, preferably aship, in the known manner, where the ship has at least one rotor sail,according to one of the embodiments described above, which is arrangedvertically on the ship in operating position and projects beyond theship. The rotor sail can furthermore be installed in an airship, where,for better controllability of the airship, the rotor sail can also beinstalled on the airship with variable orientation of the axis ofrotation of the rotary cylinder.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, will be better understood when read in conjunction withthe appended drawings. For the purpose of illustrating the invention,there are shown in the drawings embodiments which are presentlypreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 is a schematic, side view of a rotor sail according to a firstembodiment of the invention;

FIG. 2 is a schematic, side view of a rotor sail according to a secondembodiment of the invention; and

FIG. 3 is a schematic, side view of a rotor sail according to a thirdembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3 each show, in the form of a highly schematic and simplifieddiagram, a rotor sail 1 in three different embodiments. Rotor sail 1 hasa base 2, a rotary cylinder 3, which is mounted on base 2 in a mannerpermitting rotation about its longitudinal axis designed as the rotoraxis r, and whose enclosing outer surface 4 serves as a wind-exposedsurface in operation, and a drive 5 having an electric motor 6 forrotating rotary cylinder 3. Drive 5 and motor 6 are located in base 2,where rotor axis r extends into drive 5.

According to embodiments of the invention, a photovoltaic system 7 withsolar cells 8 is provided to generate electric energy for drive 5. Solarcells 8 are arranged in rotary cylinder 3 in such a way that theirphotoelectrically active layers face toward enclosing outer surface 4.Provision is furthermore made for rotary cylinder 3 to be of transparentdesign in its sleeve 9 and in its end face 10 pointing away from base 2.Moreover, end faces 10 in each case project radially beyond enclosingouter surface 4, thus creating more favorable flow conditions when thewind flows in, as is generally known. In the embodiments of rotor sail 1described here, solar cells 8 are located on the outer side of anelongated core 11 in rotary cylinder 3, where the longitudinal axis ofcore 1 is identical to rotor axis r.

In the first and second embodiments of rotor sail 1, shown in FIGS. 1and 2, core 11 has a circular transverse cross-section, while the thirdembodiment, shown in FIG. 3, has a polygonal transverse cross-section.Structurally assigned to electric drive 5 is a storage device 13 havingat least one storage battery 12 for storing the energy generated byphotovoltaic system 7, particularly the surplus electric energygenerated, for example, when motor 6 is not in operation, e.g., while aship equipped with the rotor sail is berthed.

In the two embodiments of rotor sail 1 shown in FIGS. 1 and 2, core 11is connected to rotary cylinder 3 in non-rotating fashion and is thusdriven together with rotary cylinder 3 by drive 5. In this context,rotary cylinder 3 and core 11 have common end faces 10. In theembodiment of rotor sail 1 shown in FIG. 3, on the other hand, core 11is connected to base 2 in non-rotating fashion and thus designed as astator relative to rotary cylinder 3. In this context, core 11 is heldin place via a supporting element 14.

In all the embodiments of rotor sail 1 shown, vent holes 15 are providedin end faces 10 of rotary cylinder 3 to ventilate rotary cylinder 3,particularly to extract air heated by sunlight in rotary cylinder 3.

Core 11 in FIGS. 2 and 3 is designed in upwardly tapering fashion overits height. In this context, core 11 in FIG. 2 has the form of atruncated cone with a circular cross-section, while that in FIG. 3 hasthe form of a truncated pyramid with prismatic side faces 16. As aresult, the orientation of solar cells 8, applied to core 1, relative torotor axis r is inclined at an opening angle μ, formed between thelongitudinal axis and sleeve-shaped side face 16 of core 11 having theform of a truncated cone, or the individual prismatic side faces 16 ofcore 11 having the form of a truncated pyramid. Given a customaryvertical arrangement of rotor sail 1 in operating position, as alsoillustrated in FIGS. 1 to 3, solar cells 8 are thus more oriented towardthe incident sunlight than those on core 11 shown in FIG. 1, thusincreasing their efficiency.

Deviating from the second embodiment of rotor sail 1, shown in FIG. 2,side faces 16 of core 11 in the third embodiment of rotor sail 1 are, ontheir side facing toward base 2, mounted in a joint 17 permittingpivoting in a radial pivoting direction s about a pivoting axisperpendicular to rotor axis r. As a result, opening angle μ between thecenter axis and side face 16 can be varied, and thus the orientation ofsolar cells 8 arranged on core 11 toward the sunlight. Side faces 16 aredivided into longitudinal sections 18 for structural execution. Via aradially acting pivoting device 19, the upper end of the respectivelongitudinal segment 18 in installed position is pivoted radiallyoutward in pivoting direction s, out of a home position shown in FIG. 3and into a pivoting position not shown here, in which the lateral edgesof longitudinal segments 18 are separated from each other by anincreasing distance over their height.

In the three embodiments of rotor sail 1 shown, rotor axis r isexpediently designed as a hollow axle, through which electrical lines orconductors and the like (not shown) are routed to solar cells 8, drive 5and storage device 13.

Further provided in all three embodiments is a control system 20,located in base 2, which controls the feeding of the electricitygenerated by solar cells 8 into drive 5 and into storage device 13 withstorage battery 12, as well as the tapping of electricity from storagebattery 12.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1-18. (canceled)
 19. A rotor sail comprising a base (2), a rotarycylinder (3) mounted on the base (2) in a manner permitting rotationabout a longitudinal axis of the rotary cylinder, the axis beingdesigned as a rotor axis (r), an enclosing outer surface (4) of therotary cylinder serving as a wind-exposed surface in operation, a drive(5) having an electric motor (6) for rotating the rotary cylinder (3),and a photovoltaic system (7) having solar cells (8) to generateelectric energy for the drive (5), wherein the solar cells (8) arelocated in the rotary cylinder (3) and have photoelectrically activelayers facing toward the enclosing outer surface (4), and wherein therotary cylinder (3) has a sleeve (9), which is transparent at least inan area covering the solar cells (8).
 20. The rotor sail according toclaim 19, wherein the solar cells (8) are located on an outer side of acore (11) in the rotary cylinder (3).
 21. The rotor sail according toclaim 20, wherein the core (11) has a round or polygonal transversecross-section.
 22. The rotor sail according to claim 21, wherein thecross-section is circular.
 23. The rotor sail according to claim 21,wherein the core (11) in operating position tapers prismatically orconically upward along a length of the core, and wherein the core (11)has an opening angle (μ) included between a center axis and a side face(16) of the core.
 24. The rotor sail according to claim 23, wherein thecore (11) has a form of a truncated pyramid or a truncated cone.
 25. Therotor sail according to claim 23, wherein the opening angle (μ) isvariable.
 26. The rotor sail according to claim 21, wherein the core(11) is mounted in non-rotating fashion relative to the base (2). 27.The rotor sail according to claim 21, wherein the core (11) is mountedin a manner permitting rotation about its longitudinal axis.
 28. Therotor sail according to claim 27, wherein the core (11) is connected tothe rotary cylinder (3) in non-rotating fashion.
 29. The rotor sailaccording to claim 19, wherein the solar cells (8) are located on anenclosing inner surface of the rotary cylinder (3).
 30. The rotor sailaccording to claim 19, wherein the solar cells (8) have a form ofthin-film solar cells.
 31. The rotor sail according to claim 30, whereinthe solar cells (8) comprise polymer solar cells.
 32. The rotor sailaccording to claim 19, wherein the drive (5) is located in the base (2).33. The rotor sail according to claim 19, further comprising a storagedevice (13) for storing the electric energy generated by thephotovoltaic system (7).
 34. The rotor sail according to claim 33,wherein the storage device (13) has a storage battery (12).
 35. Therotor sail according to claim 19, further comprising a control system(20), provided for open-loop and/or closed-loop control of the energygenerated by the photovoltaic system (7) and energy generatable by thephotovoltaic system (7).
 36. A ship having at least one rotor sailaccording to claim 19, wherein the rotor sail is arranged vertically onthe ship in operating position and projects beyond the ship.